1. Field of the Invention
The present invention relates to an apparatus, such as a laser plotter or a graphic arts color scanner, for recording an image. In particular, the present invention relates to an image recorder which scans an image recording surface with a plurality of parallel recording beams.
2. Description of the Prior Art
FIG. 1 is a perspective view showing a conventional laser plotter or graphic arts color scanner. The image recorder includes a recording head A and a driving unit (not shown) for moving the recording head A in the X-direction.
In operation, the laser beam B.sub.1 from a light source 50 enters a beam expander 52, its diameter is expanded, and the expanded laser beam B.sub.2 is projected onto a stop 54 having an aperture 54a. A central portion B.sub.3 of the expanded laser beam B.sub.2 is projected through the aperture 54a. The aperture 54a sharpens the edges of the image to be formed.
The laser beam B.sub.3 which passes through the stop 54 is divided into a plurality of laser beams B.sub.4 by a beam splitter 56. The laser beams B.sub.4 are individually modulated by an optical modulator system 58 in response to image signals.
A multibeam B.sub.5 from the optical modulator system 58 is reflected by reflecting mirrors 60 and 62, and then projected through a slit plate 66 toward a telecentric lens system 64 and toward a photosensitive material F which is wound on a rotating cylinder 68. Thus, the image is recorded on the photosensitive material F. The laser beams B.sub.5 are focused by the lens system 64 onto the photosensitive material F. Therefore, the conventional image recorder is advantageous in that the size of the image is not varied even if the distance between the rotating cylinder 68 and the recording head A is changed.
However, since only the central portion of the expanded laser beam B.sub.2 passes through the aperture 54a and since the extracted laser beam B.sub.3 is divided into a plurality of laser beams by the beam splitter 56, a high power light source 50 has generally been needed to be sure that the beams B.sub.4 are sufficiently intense. But this increases the size of the image recorder. This problem is also present when the light source is formed by laser diodes or the like.